I have several of their billet upper and lower receivers. I would highly recommend them. Excellent price, 7075 aluminum, great aesthetics, and some nice touches like threaded screws in place of some roll pins.
The only small complaint I have is that most of their lowers have tiny imperfections, i.e. a burr that wasn't quite machined off or a little nick in the anodizing. I am talking so small that you have to search for it, though.
"God made man, but Samuel Colt made them equal."